Air valves are commonly used to vent air from a fluid system such as water or wastewater systems. Air venting is often desired because air entrapped in the fluid system may cause pressure surges and water hammers if left unvented. The surges and water hammers can cause damage to piping and other fluid system components.
Throttling devices, such as double-acting throttling devices, are commonly used to control air flow out of the pipe system. However, current throttling devices are limited because they either have a limited throttling range and/or have only fixed-stop airflow passageways that are not self-compensating to choke flow for surge only as severity of surge increases. Small fixed passages in current throttling devices are also subject to wastewater fouling; open at a single venting air flow rate for vacuum break; and have no self-compensating mechanisms to maximize backpressure exhaust air flow for different surge conditions.